A multicast network is, generally, a network where a single sender can send data across a computer network to several users at the same time. Secure and efficient IP multicast improves efficiency of bandwidth utilization in tactical networks such as the Airborne Networks and facilitates dissemination of mission critical information among tactical edge users. Various multicast routing protocols have been proposed to provide multicast support in mobile ad hoc networks (MANETs). The majority of these routing protocols use either a mesh-based delivery structure or a tree-based delivery structure.
In mesh-based (including flooding) protocols, redundant paths are created between terminal nodes to reduce packet loss due to link failures. In networks with high terminal node mobility, this approach provides better delivery ratio of multicast data with less control data needed to maintain the delivery structure.
Tree-based multicast protocols build distribution trees from sender to receivers and generally avoid redundant paths. Protocol-Independent Multicast (PIM) protocols are tree-based protocols that have been used in wired networks to distribute multicast packets working with all underlying unicast routing protocols. In particular, the sparse mode PIM (PIM-SM) builds a shared distribution tree for all the senders originating at a designated router called a rendezvous point (RP). PIM-SM provides a capability to prune the distribution tree, where routers with local receivers can join a source-specific, shortest-path distribution tree. But the pruning process has to be initiated by the RP. PIM-SM works best in environments where group members are distributed across many regions of the network and bandwidth is scarce. Various other multicast protocols have been proposed for tree-based distribution in wireless mobile networks. These approaches have mostly been outperformed by the mesh approaches as their delivery ratios tend to suffer as terminal node mobility increases.